Radial inflow turbines, for instance those which are incorporated into small gas turbine engines or turbochargers, are usually associated with a structure commonly referred to as a scroll. The scroll is configured so as to direct hot gases exhausted from the combustion apparatus of the engine into the inlet of the radial inflow turbine. It is typically a hollow generally toroidal to component with provision for the tangential flow of hot combustion gases into its interior and the exhaustion of these gases through a suitable annular outlet into a radial inflow turbine situated at its center.
Such scrolls are, of course, exposed to very high operating temperatures and this gives rise to difficulties associated with the thermal expansion and contraction of its various regions. It has been found with traditional scroll designs that great difficulties are associated with the annular outlet of the scroll. Typically thermal expansion and contraction of the scroll can result in the axial distance across the outlet varying by as much as 10 to 12%. Such variation is highly undesirable in view of the overall effect which it has upon the efficiency of the turbine into which it directs combustion gases.